The bees are quick to notice when the cells are empty. We guess empty cells must feel quite different underfoot if you are a bee. You can watch them work on the end cells as soon as you reset the frame to the cell formed position.
We have found the bees will sense the cells are empty and begin the uncapping rewaxing and refilling process straight away. Usually they finish uncapping all the cells in a day or two. A busy hive will uncap all the cells in a day or two. If the hive is not so busy it may take longer.
We have seen a not so busy hive take a week to finish uncapping the cells on the outside frames.